1. Field of Invention
The invention relates to a key management system and, in particular, to a disk anti-copy system used between a digital device and a digital recording medium that uses a device key table (Kd Table) prepared in the device and a media key block (MKB) pre-recorded in the disk to perform fixed encryption and decryption processes.
2. Related Art
With the tremendous progress in computer hardware and software technologies and the wide multimedia applications, the technology of digital data storage has received a lot of attention. However, since the digital data can be readily dupliciated, the digital data protection stored on the recording medium is not as easy as traditional publications. The related intelligence property (IP) problems become serious. To protect the privacy and security of digital data, many anti-copy systems have been proposed.
According to the employed techniques, the normal anti-copy system can be divided into two parts: cipher algorithm and key management. Most of the prior art focuses on the improvement in the cipher algorithm. Very few people devote themselves to the new development in key management. However, anti-copy systems that involve only improvements in the cipher algorithms are very vulnerable. Therefore, it is imperative to establish a robust and complete key management mechanism, through which digital data storage security and privacy can be truly guaranteed.
The CPPM (Content Protection for Pre-recorded Media) and CPRM (Content Protection for Recorded Media) are two anti-copy system standards used in read-only recording media and rewriteable recording media. Both methods utilize the new generation technology in the cipher algorithm and key management. The main operation mode is to embed a device key table (Kd Table) into the device during manufacturing and then along with a media key block (MKB) pre-recorded in a recording medium, thus hoping to prevent the disks from being copied. The general idea is shown in FIG. 3. Nevertheless, both methods have the key-meet-in-the-middle problem. Eventually, it can be broken by hackers.
Therefore, it is of great importance for the digital data storage technology to provide an ideal key management system that makes necessary improvements in existing Kd Table and MKB. The objectives are to lower the decipher probability as well as to increase the confidentiality and security of the recorded data contents.